Given an inflow \( q_{\rm {in}} \)  and a constant time gap input \( \bar{h}_{\rm {acc}} \) , we find the equilibrium of system (REF )-() as follows, which is same as that in [1]},
\(\bar{v}=\frac{l}{(1/q_{\rm {in}})-\bar{h}_{\rm {mix}}},~~~\bar{\rho }=\frac{1}{l+\bar{h}_{\rm {mix}}\bar{v}},\) 
